Automatic model-based control scheme for stabilizing pressure during dual-gradient drilling

In this paper, we develop a methodology to maintain the bottom hole pressure with desired bounds and attenuate a kick while drilling into reservoir sections in dual-gradient drilling. An automatic switch control algorithm is developed for feedback control of sub sea pump. A kick is detected by estimation of the flow rates through the drill bit and annuls, which are obtained by new adaptive observers. When a kick is detected, the controller automatically switches to the attenuation mode, which ensures the bottom hole pressure will not go below reservoir pressure with respect to attenuating the kick. The proposed methodology is evaluated on high fidelity drilling simulator. The results show that the proposed methods are effective to stabilize the bottom hole pressure, and control the kick rapidly and safely.

► We develop a methodology to maintain the bottom hole pressure with desired bounds and attenuate a kick while drilling into reservoir sections in dual-gradient drilling.
► An automatic switch control algorithm is developed for feedback control of sub-sea pump.
► A kick is detected by estimation of the flow rates through the drill bit and annuls, which are obtained by new developed adaptive observers.
► The simulation results show that the proposed methods are effective to stabilize the bottom hole pressure, and control the kick rapidly and safely.